Materials for processing non-aqueous mixtures and methods for their preparation

ABSTRACT

The invention provides porous matrices that comprise one or more anionic surfactants that can be used in non-aqueous environments.

PRIORITY OF INVENTION

This application is a continuation under 35 U.S.C. 111(a) ofPCT/US2004/017293, filed on Jun. 2, 2004, and published in English onDec. 23, 2004 as WO 2004/110600A1, which claims the benefit under 35U.S.C. 119(e) of U.S. Provisional Patent Application Ser. Nos.60/475,281, 60/475,282, 60/475,582, and 60/474,991, all filed Jun. 2,2003, which applications and publication are incorporated herein byreference.

GOVERNMENT FUNDING AND RIGHTS

This invention was made with United States Government support undercooperative agreement 70NANB8H4028 awarded by the National Institute ofStandards and Technology (NIST). The United States Government hascertain rights in the invention.

BACKGROUND OF THE INVENTION

Semi-permeable membranes (e.g. reverse osmosis, nanofiltration,ultrafiltration, and microfiltration membranes) have a long history ofuse in separating solution components. Such membranes are a type ofseparation device that is able to retain certain substances whiletransmitting others. The components of the feed fluid that pass throughthe membrane are the “permeate” and those that do not pass through themembrane are the “retentate.” In practice, the permeate, the retentate,or both, may represent a desired product and may be used directly or besubjected to further processing.

Membranes have been widely used in a variety of water-based applicationsincluding water desalination, salt fractionation, and proteinconcentration. To a more limited extent, membranes have also beenemployed in non-water-based applications.

One limitation on the use of membranes in non-aqueous separations hasbeen the need to “condition” the membrane prior to use. Typically,membranes are prepared in aqueous environments and they are preservedwith water-based preservatives or by drying from glycerin. As a result,the membranes are not wettable with non-polar solvents or with non-polarfeed mixtures. Consequently, it is necessary to condition the membrane,for example, by contacting the membrane with a suitable intermediatesolvent, prior to use in a non-aqueous separation process. Thisconditioning method has been used to convert water wet-membranes to astate useable with hexane-based oilseed miscella and with aromatic andaliphatic hydrocarbons. See International Patent Application PublicationNumbers WO 0042138, and WO 0006526. Although this membrane conditioningtechnique has been used on a commercial scale, the method is expensive,time-consuming, and often requires the use of flammable and volatileorganic compounds.

K. D. Vos and F. O. Burris, Ind Eng Chem Prod Res Dev, 1969, 8, 84-89report that water can be evaporated from certain specific modifiedcellulose acetate reverse osmosis membranes with no loss in desalinationor physical properties by soaking the membranes in a surface activeagent before drying. The properties of the dried membranes innon-aqueous media is not discussed.

In spite of the above reports, there is currently no simple, safe,cost-effective method to preserve a membrane for use in non-aqueousapplications.

SUMMARY OF THE INVENTION

It has been found that anionic surfactants, when used as drying agents,are capable of providing a dried membrane that is wettable innon-aqueous solvents (e.g. hexane). It has also been found that anionicsurfactant treated membranes are typically wettable in water.Consequently, the invention provides a simple, inexpensive, reliablemethod for drying porous matrices, including separation membranes, toprovide dry matrices that are re-wettable in a range of aqueous andnon-aqueous environments. In one embodiment, the anionic surfactants arederived from edible foodstuffs and are especially useful for thepreservation of membranes for use in food, beverage, and pharmaceuticalapplications.

The invention also provides a method for preparing a dried porous matrixthat is wettable in non-aqueous solvents comprising treating a water-wetporous matrix with an anionic surfactant and drying to provide the driedporous matrix.

The also invention provides a porous matrix that has been dried in thepresence of an anionic surfactant.

The also invention provides a porous matrix having an anionic surfactantin or on the matrix.

The invention also provides a semi-permeable membrane prepared accordingto a method of the invention.

The invention also provides a spiral wound membrane module comprising amembrane of the invention.

The invention also provides a process for fractionating a non-aqueousmixture comprising contacting the mixture with a semi-permeable membranethat has been dried in the presence of an anionic surfactant to providepermeate that passes through the membrane and retentate that does notpass through the membrane.

The invention also provides a process for fractionating a non-aqueousmixture comprising contacting the mixture with a semi-permeable membranethat comprises an anionic surfactant to provide permeate that passesthrough the membrane and retentate that does not pass through themembrane.

The invention also provides a kit useful for performing a separation ina non-aqueous environment comprising, 1) a porous matrix that has beendried in the presence of an anionic surfactant and 2) instructions forusing the matrix (e.g. in a non-aqueous environment (e.g. without priorconditioning).

The invention also provides a kit useful for performing a separation ina non-aqueous environment comprising, 1) a porous matrix having ananionic surfactant in or on the matrix, and 2) instructions for usingthe matrix in a non-aqueous environment (e.g. without priorconditioning).

The invention also provides a permeate or a retentate prepared with amembrane or kit of the invention or prepared by a method of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Specific and preferred values for terms, ranges, etc. identified hereinare for illustration only; they do not exclude other defined values orother values identified herein.

Terms

The term “porous matrix” includes membranes such as reverse osmosis,nanofiltration, ultrafiltration, and microfiltration membranes, as wellas porous beads, chromatography media, paper, filtration media, and thelike. The invention provides a variety of porous matrices that have beendried in the presence of or that comprise an anionic surfactant. Suchmatrices can be used directly in non-aqueous environments withoutconditioning.

“Wetting” is a well known term that refers to a process in which a fluidspreads upon the external surface of a non-porous material and upon theexternal and internal surfaces of a porous or semi-porous material.

Anionic Surfactants

The meaning of the term “anionic surfactant” is well understood. Forexample, see Kirk-Othmer, Concise Encyclopedia of Chemical TechnologyI,John Wiley and Sons, New York, 1985, 1142-1146.

Anionic surfactants typically have a low energy chemical moiety (e.g., ahydrophobic moiety) and a polar moiety which is anionic or capable offorming an anion. The term includes carboxylates, (RCOO—, wherein R istypically a C₉-C₂₁ branched or unbranched, saturated or unsaturatedhydrocarbon chain), acylated protein hydrolysates, sulfonates, sulfates,sulfated products, phosphatides, and phosphate esters. Specific examplesof anionic surfactants include palmitate salts (e.g. sodium palmitate)and sodium lauryl sulfate.

In one specific embodiment of the invention the anionic surfactant isderivable from an animal product.

In one specific embodiment of the invention the anionic surfactant isderivable from a vegetable product.

In one specific embodiment of the invention the anionic surfactant ispotassium oleate or sodium dodecylsulfate.

In another specific embodiment of the invention the anionic surfactantis not potassium oleate or sodium dodecylsulfate.

Non-Aqueous Mixture

The term “non-aqueous” includes, 1) a liquid capable of being fullymiscible with hexane in a 50:50 proportion at 25° C., 2) a liquid thatcontains less than 50% water, and 3) a liquid that contains more than10% of an organic substance.

In one specific embodiment the non-aqueous mixture can be any vegetableoil miscella containing phospholipids. The vegetable oil miscellagenerally comprises solvent and crude vegetable oil. The vegetable oilmiscella is generally obtained by solvent extraction of vegetable seeds.Techniques for solvent extraction of vegetable seeds are well known andare described, for example, in Bailey's Industrial Oil and Fat Products,5^(th) Edition, edited by Y. H. Hui, New York, Wiley, 1996, and Handbookof Soy Oil Processing and Utilization, St. Louis, Mo., American SoybeanAssociation, Champaign, Ill., American Oil Chemists' Society, thedisclosures of which are incorporated herein by reference. Typically,vegetable seeds suitable for use in the present invention include soyabean, corn, ground nut, olives, linseed, rapeseed, sunflower seed,safflower seed, cottonseed oil, and grape seed.

Any suitable solvent may be used in the process. Exemplary solvents usedin the process include inert hydrocarbons such as alkanes, alcohols,cycloalkanes, and simple aromatic hydrocarbons, for example, benzene andits homologues containing alkyl substituents having up to four carbonatoms, toluene, and xylenes. The alkane and alcohol solvents can bestraight chain or branched. Exemplary straight chain or branched alkanesand alcohols include hexane such as n-hexane and isohexane, ethanol,n-propyl alcohol, isopropyl alcohol, and mixtures thereof. The amount ofsolvent present in the vegetable oil miscella may vary depending uponthe particular solvent extraction design utilized. In general, it isexpected that the vegetable oil miscella will include an amount ofsolvent of from about 45 percent by weight (wt. %) to about 90 wt. %. Inone specific embodiment, the vegetable oil miscella will include anamount of solvent of from about 50 wt. % to about 85 wt. %.

In one specific embodiment of the invention the non-aqueous fluidmixture is a vegetable oil miscella.

In another specific embodiment of the invention the non-aqueous fluidmixture is an oil miscella.

In another specific embodiment of the invention the non-aqueous fluidmixture comprises a vegetable oil miscella.

In another specific embodiment of the invention the non-aqueous fluidmixture comprises an oil miscella.

In another specific embodiment of the invention the non-aqueous fluidmixture is not a vegetable oil miscella.

In another specific embodiment of the invention the non-aqueous fluidmixture is not an oil miscella.

In another specific embodiment of the invention the non-aqueous fluidmixture does not comprise a vegetable oil miscella.

In another specific embodiment of the invention the non-aqueous fluidmixture does not comprise an oil miscella.

Semi-Permeable Membranes

The term “semi-permeable membrane” includes any semi-permeable materialwhich can be used to separate components of a feed fluid into a permeatethat passes through the material and a retentate that is rejected orretained by the material. For example, the semi-permeable material maycomprise organic polymers, organic co-polymers, mixtures of organicpolymers, or organic polymers mixed with inorganics. Suitable organicpolymers include polysulfones; poly(styrenes), includingstyrene-containing copolymers such as acrylonitrile-styrene copolymers,styrene-butadiene copolymers and styrene-vinylbenzylhalide copolymers;polycarbonates; cellulosic polymers, such as cellulose acetate-butyrate,cellulose propionate, ethyl cellulose, methyl cellulose, nitrocellulose,etc.; polyamides and polyimides, including aryl polyamides and arylpolyimides; polyethers; poly(arylene oxides) such as poly(phenyleneoxide) and poly(xylene oxide); poly(esteramide-diisocyanate);polyurethanes; polyesters (including polyarylates), such aspoly(ethylene terephthalate), poly(alkyl methacrylates), poly(alkylacrylates), poly(phenylene terephthalate), etc; polysulfides; polymersfrom monomers having alpha-olefinic unsaturation other than mentionedabove such as poly(ethylene), poly(propylene), poly(butene-1),poly(4-methyl pentene-1), polyvinyls, e.g. poly(vinyl chloride),poly(vinyl fluoride), poly(vinylidene chloride), poly(vinylidenefluoride), poly(vinyl alcohol), poly(vinyl esters) such as poly(vinylacetate) and poly(vinyl propionate), poly(vinyl pyridines), poly(vinylpyrrolidones), poly(vinyl ethers), poly(vinyl ketones), poly(vinylaldehydes) such as poly(vinyl formal) and poly(vinyl butyral),poly(vinyl amides), poly(vinyl amines), poly(vinyl urethanes),poly(vinyl ureas), poly(vinyl phosphates), and poly(vinyl sulfates);polyallyls; poly(benzobenzimidazole); polyhydrazides; polyoxadiazoles;polytriazoles; poly(benzimidazole); polycarbodiimides; polyphosphazines;etc., and interpolymers, including block interpolymers containingrepeating units from the above such as terpolymers ofacrylonitrile-vinyl bromide-sodium salt of para-sulfophenylmethallylethers; and grafts and blends containing any of the foregoing. Suchorganic polymers can optionally be substituted, for example, withhalogens such as fluorine, chlorine and bromine; hydroxyl groups; loweralkyl groups; lower alkoxy groups; monocyclic aryl; lower acyl groupsand the like.

Semi-permeable membranes can also include modified versions of organicpolymers. For example, organic polymers can be surface modified, surfacetreated, cross-linked, or otherwise modified following polymerformation, to provide additional semi-permeable materials that can beincluded in semi-permeable membranes. For example, see U.S. Pat. Nos.4,584,103, 4,906,379, 4,477,634, 4,265,959, and 4,147,745 for examplesof modified organic polymers.

In one preferred embodiment, the semi-permeable membrane comprises anengineering polymer such as, for example, a polysulfone,polyethersulfone, polyimide, polyamide, polyacrylonitrile,polycarbonate, or polyvinylidene-fluoride. Membranes comprising suchpolymers are typically stable at higher temperatures than othermembranes such as cellulose acetate containing membranes. In a morepreferred embodiment, the semi-permeable membrane comprises an aromaticpolysulfone, polyethersulfone, polyimide, polyamide, polyacrylonitrile,polycarbonate, or polyvinylidene-fluoride. Again, such aromatic polymersare typically preferred due to their stability, and in particular, dueto their temperature stability.

In another embodiment, the semi-permeable membrane comprises apolysulfone, polyethersulfone, polyvinylidene-fluoride,polytetrafluoroethylene, polyacrylonitrile, polycarbonate, cellulose,cellulose acetate, polyimide, polyaramide, nylon, polyamide,polysulfonamide, or a polyarylketone, or a co-polymer or modifiedversions of such a material.

In one embodiment, the semi-permeable membrane is not cellulose acetate.In another embodiment, the semi-permeable membrane does not comprisecellulose acetate.

Microfiltration membranes are those membranes with pores greater thanabout 0.1 microns in diameter. The upper pore size limitation of themicrofiltration membranes is not well defined, but can be considered tobe about 10 microns. Materials with pore sizes larger than about 10microns are generally not referred to as membranes. Microfiltrationmembranes are commonly used to retain small particulates and microbes.Typically, these membranes permeate smaller components, such as simplesalts and dissolved organic materials having a molecular weight of lessthan about 1,000,000 grams per mole. Microfiltration membranes usuallypossess the highest water permeability of the four classes of membranes,due to their large pore diameters as well as their typical high poredensity. The pure water permeability (A-value) of these membranes iscommonly greater than about 5,000. The units of A-value are 10⁻⁵ cm³ ofpermeate per cm² of membrane area per second of test time per atmosphereof driving pressure. Ultrafiltration membranes typically arecharacterized by pore sizes of from about 0.1 micron to about 1nanometer.

Ultrafiltration membranes are commonly classified by their ability toretain specific sized components dissolved in a solution. This isreferred to as the molecular weight cut-off (MWCO), and the MWCO profileof a membrane may be determined using ASTM Method E1343-90.Ultrafiltration membranes are commonly used to retain proteins,starches, and other relatively large dissolved materials whilepermeating simple salts and smaller dissolved organic compounds. Thewater permeability of ultrafiltration membranes is commonly in the rangeof from about A=100 to about A=5000. In a preferred embodiment of theinvention, the semi-permeable membrane is an ultrafiltration membrane,for example, an ultrafiltration membrane as described in the examplesbelow.

Nanofiltration membranes typically are defined as membranes whichpossess the ability to fractionate small compounds (i.e., those withmolecular weights less than 1000). The small compounds are often salts,and nanofiltration membranes are commonly used to permeate monovalentions while retaining divalent ions. Nanofiltration membranes typicallyposses ionized or ionizable groups.

Although not wishing to be bound by theory, it is believed that thenanofilters can affect the separation of ionic materials through acharge-based interaction mechanism. Nanofiltration membranes also can beused to separate uncharged organic compounds, sometimes in solventsother than water. The water permeability of nanofiltration membranes iscommonly in the range of from about A=5 to about A=50.

Reverse osmosis membranes can retain all components other than thepermeating solvent. Like nanofiltration membranes, reverse osmosismembranes can contain ionic functional groups. Reverse osmosis membranesare commonly used to remove salt from water and concentrate smallorganic compounds. The water permeability of reverse osmosis membranesis commonly in the range of from about A=2 to about A=20.

Although the mechanisms that govern membrane performance are not exactlydefined, some basic theories have been postulated. A good review of somemembrane transport theories can be found in, J. G. Wijmans, R. W. Baker,Journal of Membrane Science, 1995, 107, 1-21.

In addition, semi-permeable membranes also can be classified by theirstructure. Examples are symmetric, asymmetric, and composite membranes.Symmetric membranes are characterized by having a homogeneous porestructure throughout the membrane material. Examples of symmetricmembranes include some microfiltration membranes, many ceramicmembranes, and track-etched microporous membranes.

Asymmetric membranes are characterized by a heterogeneous pore structurethroughout the membrane material. These membranes usually posses a thin“skin” layer having a smaller pore structure than the underlyingmaterial. Many commercially available ultrafiltration membranes possesan asymmetric structure.

Membranes of the invention typically have a pore size of less than about0.2 microns. In a specific embodiment, membranes of the invention have apore size of less than about 0.05 microns. In another specificembodiment, membranes of the invention have a pore size of from about 50nanometers to about 3 nanometers. In another specific embodiment,membranes of the invention have a pore size of from about 50 nanometersto about 0.5 nanometers. In yet another specific embodiment, membranesof the invention have a pore size of from about 20 nanometers to about 1nanometer.

The term “pore size” means the mode diameter of the pores in thematerial.

“Composite membranes” have at least one thin film (matrix) layered on aporous support. The thin film is usually a polymer of a thickness ofless than about 20 microns, and often less than about 1 micron. Theporous support should be relatively stable to the feed solution,pressure, and temperature, and should be compatible with the thin film.The porous support is commonly a polymeric ultrafiltration ormicro-filtration membrane, such as a polysulfone, polyethersulfone,polyvinylidene fluoride, polyvinylchloride, ceramic, or porous glass.

In one specific embodiment, the invention provides a porous matrix thatis a semi-permeable membrane.

In one specific embodiment, the invention provides a semi-permeablemembrane that is a composite membrane.

In one specific embodiment, the invention provides a composite membranethat comprises a polysulfone, polyethersulfone, polyvinylidene-fluoride,polytetrafluoroethylene, polyacrylonitrile, polycarbonate, cellulose,cellulose acetate, polyimide, polyaramide, nylon, polyamide,polysulfonamide, polyarylketone, or a co-polymer or a modified polymerthereof.

In one specific embodiment, the invention provides a composite membranethat comprises a polysulfone, polyethersulfone, polyvinylidene-fluoride,polytetrafluoroethylene, polyacrylonitrile, polycarbonate, cellulose,polyimide, polyaramide, nylon, polyamide, polysulfonamide,polyarylketone, or a co-polymer or a modified polymer thereof.

In one specific embodiment, the invention provides a composite membranethat does not comprise a cellulose acetate film.

In one specific embodiment, the invention provides a composite membranecomprises a polyethersulfone film.

In one specific embodiment, the invention provides a membrane that is areverse osmosis membrane, nanofiltration membrane, ultrafiltrationmembrane, or microfiltration membrane.

In one specific embodiment, the invention provides a membrane that is anultrafiltration membrane.

In one specific embodiment, the invention provides a membrane that is ananofiltration membrane.

In one specific embodiment, the invention provides a membrane that is areverse-osmosis membrane.

In one specific embodiment, the invention provides a composite membranethat has a porous support that is an ultrafiltration or amicrofiltration membrane.

In one specific embodiment, the invention provides a composite membranethat has a porous support that is an ultrafiltration or amicrofiltration membrane, wherein the ultrafiltration or microfiltrationmembrane comprises a polysulfone, polyethersulfone, polyvinylidenefluoride, polyvinylchloride, ceramic, or porous glass.

In one specific embodiment, the invention provides a composite membranethat has a porous support that is an ultrafiltration or amicrofiltration membrane, wherein the ultrafiltration or microfiltrationmembrane comprises a polysulfone, polyethersulfone, polyvinylidenefluoride, or polyvinylchloride.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a pore size of less than about 0.1 microns.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a pore size of less than about 0.05 microns.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a pore size of from about 50 nanometers to about 1nanometer.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a pore size of from about 50 nanometers to about 0.5nanometers.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a pore size of from about 10 nanometers to about 1nanometer.

In one specific embodiment, the invention provides a semi-permeablemembrane that has an A-value of less than about 10,000.

In one specific embodiment, the invention provides a semi-permeablemembrane that has an A-value of less than about 5,000.

In one specific embodiment, the invention provides a semi-permeablemembrane that has an A-value of less than about 2,000.

In one specific embodiment, the invention provides a semi-permeablemembrane that has an A-value of less than about 500.

In one specific embodiment, the invention provides a semi-permeablemembrane that has an A-value of less than about 30.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a molecular weight cutoff of less than about1,000,000.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a molecular weight cut-off of less than about 500,000.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a molecular weight cut-off of less than about 100,000.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a molecular weight cut-off of less than about 30,000.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a molecular weight cut-off of less than about 10,000.

In one specific embodiment, the invention provides a semi-permeablemembrane that has a molecular weight cut-off of less than about 3,000.

In one specific embodiment, the invention provides a semi-permeablemembrane that is wettable in a liquid that has a surface tension of lessthan 50 dyne/cm.

In one specific embodiment, the invention provides a semi-permeablemembrane that is wettable in a liquid that has a surface tension of lessthan 40 dyne/cm.

In one specific embodiment, the invention provides a semi-permeablemembrane that is wettable in a liquid that has a surface tension of lessthan 30 dyne/cm.

In one specific embodiment, the invention provides a semi-permeablemembrane that is wettable in a liquid that has a surface tension of lessthan 25 dyne/cm.

In one specific embodiment, the invention provides a semi-permeablemembrane that is wettable in a liquid that has a surface tension of lessthan 20 dyne/cm.

General Matrix and Membrane Preparation

Membranes can be prepared using methods that are known in the field, forexample, as described in the Handbook of Industrial Membrane Technology,1990, edited by Mark C. Porter, ISBN 0-8155-1205-8. Membranes of theinvention are typically contacted with an anionic surfactant prior todrying. The anionic surfactant can be present in a solution used to formthe membrane or can be added as part of a post-treatment process.

When an anionic surfactant is added as a post-treatment, the membranecan be contacted with the anionic surfactant at any concentration andfor any amount of time suitable to provide a membrane that is wettablein a non-aqueous solvent. Typically, the membrane is contacted with theanionic surfactant for a time up to about 2 hours (e.g., for about 20seconds to about 60 minutes) at an anionic surfactant concentration offrom about 1% to its water solubility. However, longer contact times ordifferent concentrations of anionic surfactant can be used.

The membrane can typically be dried under any condition suitable toprovide a membrane that can be used directly in a non-aqueous solvent.For example, the membranes can be dried using airflow, reduced pressure,or elevated temperature, or any combination thereof, provided that thetemperature of the drying process does not reach a point where themembrane is significantly damaged. With membranes that are resistant toat least 120° C., many membranes can be dried in an oven at 90 to 120°C. for about two to about six minutes.

Spiral Wound Elements

One common device that utilizes semi-permeable membranes (e.g., RO, NF,and UF membranes) is a spiral wound membrane element. Such a spiralwound element typically comprises a leaf, or a combination of leaves,wound around a central tube with a feed spacer material. Such spiralwound membrane elements and methods for their preparation are wellknown. For example see Bray (U.S. Pat. No. 3,417,870) and Lien (U.S.Pat. No. 4,802,982). The invention also provides a spiral wound membraneelement comprising a semi-permeable membrane of the invention. Suchelements are particularly useful for separating (e.g., purifying)non-aqueous feed streams.

Separations

In one specific embodiment, the invention provides a method forfractionating a non-aqueous fluid mixture comprising contacting thefluid mixture with a semi-permeable membrane of the invention to providea permeate that passes through the membrane and retentate that does notpass through the membrane. In the practice of such a method, membranesof the invention (e.g., membranes that have been dried in the presenceof an anionic surfactant or that comprise an anionic surfactant) can beused directly (e.g., with reduced or no need for conditioning beforecontact with the non-aqueous mixture). The membranes can typically beused to fractionate any non-aqueous mixture.

In one embodiment of the invention a vegetable oil miscella is passedthrough a semi-permeable membrane resulting in a phospholipid containingretentate and a phosphorus reduced permeate. If desired, the vegetableoil miscella from the first semi-permeable membrane can be passedthrough at least one additional semi-permeable membrane. The phosphorusreduced permeate is typically less than about 5 ppm to about 10 ppmphosphorus. The phospholipid containing retentate is a fluid lecithinproduct. If desired, the phospholipid containing retentate can befurther processed to obtain a deoiled lecithin product. Where thevegetable oil miscella contains solids such as meal fines obtained fromseed hulls, dirt, sand grit, and the like, the vegetable oil miscellamay be prefiltered prior to passing the vegetable oil miscella throughthe semi-permeable membrane of the present process to avoid clogging thesemi-permeable membrane.

The lecithin product according to the invention can be used in anyapplication where lecithin has been used. In addition, the lecithinproduct according to the invention can be used in any other applicationswhere desirable. For example, the lecithin product according to theinvention can be used as an emulsifier, surfactant, stabilizer,releasing agent, wetting agent, dispersing agent, lubricant, viscositycontrol agent, crystallization agent, softening agent, emollient,anti-dusting agent, and high nutritional ingredient. Variousapplications in which the lecithin product according to the inventioncan be used include food applications, feed applications, technicalapplications, cosmetic applications, pharmaceutical, and nutraceuticalapplications. Exemplary food applications include chocolate, chocolatederivatives, bakery, confectionary, icings, dairy products, cheeseproducts, pasta products, margarine, shortening, fat mixtures,emulsions, spray oils, dressings, instantizing of cacao, milk, non dairyprotein powders, release agents, soups, sauces, mayonnaises, dressings,meats, gravies, canned meats, meat analogues, bread improvers,beverages, energy drinks, snacks, desserts (such as, ice cream andbars), meal improvers, bread improvers, chewing gum, colors, flavormixes, emulsifier mixes, baby food, and antioxidants. Exemplary feedapplications include emulsifiers and sources of high nutritional valuein feed for, for example, fish, shrimp, calves (as milk replacer), pigs,sows, piglets, pets, mink, and poultry. Exemplary technical applicationsincludes as a dispersing agent in, for example, paints, inks, coatings,magnetic tapes, and discs, as a softening agent in, for example, leatherand textiles, as an emulsifier in, for example, crop protection andagrochemicals, as lubricants, oils, adhesives, adsorbents, flocculants,corrosion inhibitors, ceramics, glass, detergents, metal processing,paper, petroleum products, photocopying, photography, polymers, rubbers,and textiles. Exemplary cosmetic applications include as a dispersingagent in lipstick and nail polish, and as an emulsifier/stabilizer inshampoos, creams, and lotions. Exemplary pharmaceutical and/ornutraceutical applications include as a natural source of phospholipids.Exemplary phospholipids include phosphatidylcholine and vitamin E.

The lecithin product according to the invention can be used as astarting material for derived processes and products, such as, deoiledlecithin, phospholipids fractions, enzymatical modifications, chemicalmodifications, and compounded products. Exemplary chemical modificationsinclude hydroxylation, acetylation, interesterification, andhydrogenation. Exemplary compounded products include use on a carrierand with emulsifiers.

In one specific embodiment the invention provides a method for treatingvegetable oil miscella comprising passing the miscella through amembrane comprising a semi-permeable membrane comprising a componentselected from the group consisting of sodium dodecyl sulfate andpotassium oleate to obtain a rententate and a permeate.

The invention will now be illustrated by the following non-limitingExamples. In Examples 1 through 4, the percent phospholipids rejectionis calculated from the following equation:

${\%\mspace{14mu}{Phospholipid}\mspace{20mu}{Rejection}} = {\frac{\begin{matrix}\left( {{{Retentate}\mspace{14mu}{phospholipids}\mspace{14mu}{concentration}} -} \right. \\\left. {{Permeate}\mspace{14mu}{phospholipids}\mspace{14mu}{concentration}} \right)\end{matrix}\mspace{14mu}}{{Retentate}\mspace{14mu}{phospholipids}\mspace{14mu}{concentration}} \times 100}$

Example 1

A vegetable oil miscella was treated to remove phospholipids from thevegetable oil. The vegetable oil miscella was passed through a 75 micronscrap surface screen filter and then through a 6 micron absolute pleatedfilter, which was coated with 0.1% diatomaceous earth. The 75 micronscreen filter is available from Solution Technology, Wisconsin, and the6 micron pleated filter was purchased from Osmonics, Inc., Minnetonka,Minn. The filtrate was then passed through two dead-end filters having apore size of 0.45 micron and 0.2 micron respectively. The 0.45 microndead-end filter was purchased from Parker Hannifin, Indianapolis, Ind.,and the 0.2 micron dead-end filter was purchased from Osmonics, Inc.,Minnetonka, Minn.

The resulting vegetable oil miscella comprising 79.7 wt. % hexane, 2.6wt. % phospholipids, and 17.7 wt. % oil was passed through two of thesame spiral wound 4 inch by 40 inch semi-permeable membranes of thepresent invention. The semi-permeable membrane was a polyethersulfoneultrafiltration membrane comprising potassium oleate and having anA-value of 1,870 10⁻⁵ cm³ of permeate per cm² of membrane area persecond of test time per atmosphere of driving pressure. Thesemi-permeable membrane was prepared by immersing a polyethersulfone,ultrafiltration membrane in a solution of 16% potassium oleate, 10%ethanol and 74% deionized water for 15 to 20 seconds, then drained anddried in a 100° C. oven for 3 minutes. The vegetable oil miscella waspassed through the spiral wound membrane elements for a period of oneminute at a temperature of 39.4° C. and at a circulation rate of 20gallons per minute. The filtration rate obtained from the 2semi-permeable membranes was 10.46 kilogram per minute at an averagetransmembrane pressure of 0.9 psi. There was produced a phospholipidcontaining retentate comprising 10.66% phospholipid and a permeatecomprising 56.6 ppm phosphorus on a hexane-free oil basis. It wasobserved that the value of the permeate flux was 66.9 liter/hour/meter²(9.56 kilogram/hour/meter² on a hexane-free oil basis). From the dataabove, it was observed that the semi-permeable membrane of the presentinvention provided 99.84% rejection of the phospholipids.

Example 2

The procedure of Example 1 was followed, except that the vegetable oilmiscella comprising 80.6 wt. % hexane, 2.6 wt. % phospholipids, and 16.8wt. % oil was passed through the semi-permeable membrane for a period of15 minutes at a temperature of 44.7° C. The filtration rate obtainedfrom the 2 membranes was 11.14 kilogram per minute at an averagetransmembrane pressure of 3.2 psi. There was produced a phospholipidcontaining retentate comprising 15.34% phospholipid and a permeatecomprising 49.9 ppm phosphorus on a hexane-free oil basis. It wasobserved that the value of the permeate flux was 71.6 liter/hour/meter²(9.7 kilogram/hour/meter² on a hexane-free oil basis). From the dataabove, it was observed that the semi-permeable membrane of the presentinvention provided 99.81% rejection of the phospholipids.

Example 3

The procedure of Example 1 was followed, except that the vegetable oilmiscella comprising 79.5 wt. % hexane, 2.6 wt. % phospholipids, and 17.9wt. % oil was passed through the semi-permeable membrane for a period of35 minutes at a temperature of 47.7° C. The filtration rate obtainedfrom the 2 membranes was 11.82 kilogram per minute at an averagetransmembrane pressure of 5.7 psi. There was produced a phospholipidcontaining retentate comprising 28.66% phospholipid and a permeatecomprising 60.0 ppm phosphorus on a hexane-free oil basis. It wasobserved that the value of the permeate flux was 75.7 liter/hour/meter²(10.93 kilogram/hour/meter² on a hexane-free oil basis). From the dataabove, it was observed that the semi-permeable membrane of the presentinvention rejected 99.37% phosphorus in 35 minutes, that is, it wasobserved that the membrane provided 99.37% rejection of thephospholipids.

Example 4

The procedure of Example 1 was followed, except that the vegetable oilmiscella comprising 78.9 wt. % hexane, 2.6 wt. % phospholipids, and 18.5wt. % oil was passed through the semi-permeable membrane for a period of55 minutes at a temperature of 49.2° C. The filtration rate obtainedfrom the 2 membranes was 12.9 kilogram per minute at a transmembranepressure of 6.7 psi. There was produced a phospholipid containingretentate comprising 28.66% phospholipid and a permeate comprising 51.2ppm phosphorus on a hexane-free oil basis. It was observed that thevalue of the permeate flux was 74.9 liter/hour/meter² (11.17kilogram/hour/meter² on a hexane-free oil basis). From the data above,it was observed that the semi-permeable membrane of the presentinvention rejected 99.46% phosphorus in 55 minutes.

Example 5

A knife-over-roll coating system was used to coat a dope solution ofpolyethersulfone on a web of polyester backing material. The web wasthen run through a water tank to cause the phase-inversion membraneformation process, resulting in a membrane. The membrane was then runthrough a second water tank to remove residual solvents from the coatingprocess.

The produced membrane was evaluated in an Amicon 8200 stirred cell at 20psi, using DI water for the flux measurement and an aqueous solution ofdextrans for determination of the membrane molecular weight cut-off(MWCO) using a procedure adapted from ASTM Method E1343-90. Data areshown in Table 3. This membrane was employed as a “wet-control” of themembrane's performance attributes for comparison of drying with orwithout various chemical agents in solution.

Samples of the membrane were cut from the master roll of membrane andtreated with a solution of potassium oleate (as indicated in Table 3)dissolved in 10% ethanol and DI water. The membrane samples wereimmersed in the drying solution for 15-20 seconds, then drained andplaced into a 100° C. oven for 3 minutes, then were removed and left inambient air conditions at least 18 hours prior to testing. Dried sampleswere tested for flux and MWCO in the same manner as the wet controlmembrane.

TABLE 3 Performance of PES-1 versus drying with specified chemicalagents in solution. % Potassium MWCO @ 90% Oleate Flux, 1 mh DextranRejection Wet control 590 56,000-91,000  0% 20 Not determined  5% 40833,000-46,000 10% 438 39,000-48,000 14% 615 78,000-91,000 16% 64065,000-84,000 18% 680 66,000-85,000

Example 6

The membrane described in Example 5, which was dried from the 16%potassium oleate solution, was tested in a hexane-based miscelladegumming application. This membrane gave identical performanceproperties on a hexane-based miscella degumming application to a wetcontrol membrane sample that had been solvent exchanged (conditioned)into hexane by successive 30 minute soaks in isopropanol, 50/50hexane/isopropanol, and 90/10 hexane/soybean oil. A membrane similardried without the aid of a drying agent gave extremely poor performance,and a similarly membrane sample dried using a traditional glycerindrying technique yielded no significant permeate flow. Accordingly, themembrane of the invention could be used in the hexane-based miscelladegumming application without prior conditioning.

Example 7

A polyethersulfone solution was cast on a polyester substrate and thenplaced in contact with water to form the polyethersulfone into a solidporous coating. The water permeability, or A-value, of this membrane wasfound to be 1530. The material was then placed into a solution of 90%water and 10% sodium dodecyl sulfate (Aldrich Catalog #85,192-2)followed by drying at 80° C. for 4 minutes. The resulting membrane ischaracterized by a water permeability value of 1500, which isessentially the same water permeability as the undried membrane, basedon the limits of membrane and test variability. Thus, the waterpermeability of the dried membrane was not significantly diminished.

Example 8

A polyethersulfone membrane is formed in the classical phase inversionprocess (e.g., web-handling equipment comprised of a knife-over-rollmetering hopper, coagulation and rinse tank was used to deposit a layerof polymer solution onto a polyester nonwoven support fabric at aconstant web speed). This coated fabric is subsequently coagulated in apure water bath, and rinsed to remove solvent residuals.

The resulting membrane is evaluated in an Amicon 8200 stirred cell,using DI water for flux and dextrans for MWCO determination by a methodadapted from ASTM Method E1343-90. This membrane is employed as a“wet-control” of the membrane's performance attributes for comparison ofdrying with or without anionic surfactants in solution.

Samples of the membrane are cut from the master roll of membrane andtreated with a solution of an anionic surfactant. The membrane samplesare immersed into the drying solution for 15-20 seconds, drained, placedinto a 100° C. oven for 3 minutes, removed, and left in ambient airconditions at least 18 hours prior to testing. Dried samples are testedfor flux and MWCO in the same manner as the wet control membrane forcomparison.

All publications, patents, and patent documents (including U.S.Provisional Patent Application Ser. Nos. 60/475,281, 60/475,282,60/475,582, and 60/474,991) are incorporated by reference herein, asthough individually incorporated by reference. The invention has beendescribed with reference to various specific and preferred embodimentsand techniques. However, it should be understood that many variationsand modifications may be made while remaining within the spirit andscope of the invention.

1. A method for fractionating a non-aqueous mixture comprisingcontacting the mixture with a semi-permeable membrane that has beendried in the presence of an anionic surfactant to provide permeate thatpasses through the membrane and retentate that does not pass through themembrane, wherein the non-aqueous fluid comprises an oil miscellamixture.
 2. The method of claim 1 wherein the anionic surfactant ispotassium oleate or sodium dodecyl sulfate.
 3. The method of claim 1wherein the semi-permeable membrane is a composite membrane.
 4. Themethod of claim 3 wherein the composite membrane comprises apolysulfone, polyethersulfone, polyimide, polyamide, polyacrylonitrile,polycarbonate, or polyvinylidene-fluoride film.
 5. The method of claim 3wherein the composite membrane comprises an aromatic polysulfone,polyethersulfone, polyimide, polyamide, polyacrylonitrile,polycarbonate, or polyvinylidene-fluoride film.
 6. The method of claim 3wherein the composite membrane comprises a polyethersulfone film.
 7. Themethod of claim 1 wherein the semi-permeable membrane has a pore size ofless than about 0.1 microns.
 8. The method of claim 1 wherein thesemi-permeable membrane has a pore size of from about 50 nanometers toabout 0.5 nanometers.
 9. The method of claim 1 wherein thesemi-permeable membrane has an A-value of less than about 10,000. 10.The method of claim 1 wherein the semi-permeable membrane has an A-valueof less than about 2,000.
 11. The method of claim 1 wherein thesemi-permeable membrane has a molecular weight cut-off of less thanabout 1,000,000.
 12. The method of claim 1 wherein the semi-permeablemembrane has not been conditioned prior to contact with the mixture. 13.The method of claim 1 wherein the oil miscella is a vegetable oilmiscella.